It is known that the mechanical properties of cement are improved by incorporating asbestos fibers therein. Asbestos offers great advantages in such applications, due to its fiber structure and its resistance to the alkalinity of cement. The pertinent relationships between asbestos and various settable mineral materials have been known for some time. Such relationships have long been considered and explored as they relate to the fabrication of asbestos fiberboard. Despite the advantages of asbestos, there are health hazards associated both with the production and also the processing of asbestos fibers. Fine asbestos fibers, when inhaled, trigger a carcinogenic effect in the body's pulmonary system. This situation forced industry to find a substitute for the asbestos fiber skeleton traditionally used to improve the mechanical properties of settable mineral materials.
Many suggestions have been made for manufacturing sheet materials comparable to those made with asbestos. For example, fibers with a cellulose and synthetic polymer base were suggested. However, such fibers are characterized by insufficient chemical durability. Furthermore, the mechanical properties are unsatisfactory in that the rheological changes in the structure of the hydrated cement deviate too much from those of the fiber material. Also, considerable difficulties arise in obtaining a uniform distribution of the reinforcement fibers in the mineral material. These difficulties, as they relate to, e.g., incorporation of the fibers into a cement mixture, are associated particularly with the specific properties of the available polymer materials, whose properties differ substantially from those of natural asbestos fibers.
It is an object of the present invention to provide a shaped body of a polymer material embedded in a mineral material, which can be manufactured without the above-mentioned difficulties, and which also exhibits qualities that are mechanically as well as chemically comparable to those exhibited by the above-mentioned asbestos/cement fiber sheets.